Investigation of oil and water migrations in lacustrine oil shales using 20 MHz 2D NMR relaxometry techniques

Abstract

The behavior of oil and water in tight rocks can change the distribution of oil or water in pores, which affects the production of crude oil. Nuclear Magnetic Resonance (NMR) method is an effective and non-destructive tool for evaluating rocks with comparison and analysis both quantitatively and qualitatively. In our study, 20 MHz NMR Relaxometry is used as a key technique to study the changes of water and oil behaviors in Chinese lacustrine Qingshankou shales under different saturated states (imbibition and evaporation without pressure). The results show that variation in different proton populations (water, oil and organic) can be distinguished using 2D T1–T2 maps. The comparison among T1-T2 maps with different saturated states shows that different signal regions changed during oil and water migrations, which the 1D NMR Relaxometry may be not easy to approach. Combined with the pyrolysis analysis, T2 shift and differences of signal regions in T1-T2 maps can reflect properties such as wettability and composition (organic matter, clay and magnetic minerals) to some extent. This study provides better insight into oil and water behaviors in lacustrine oil shales with further understanding of 20 MHz NMR 2D T1-T2 maps both in qualitative and quantitative analysis.